Rotary screening drum



Dec. 5, '1950 K. R. LINDBLAD ROTARY SCREENING DRUM 2 Sheets-Sheet 1Filed April 19, 1946 Dec. 5, 1950 K. R. LINDBLAD ROTARY SCREENING DRUM 2Sheets-Sheet 2 Filed April 19, 1946 Patented Dec. 5, 1950 ROTARYSCREENING DRUM Karl Roland Lindblad, Sundsbruk, Sweden, as-

signor to Svenska Cellulosa Aktiebolaget, Stockholm, Sweden, ajoint-stock company of Sweden Application April 19, 1946, Serial No.663,393 In Sweden April 25, 1945 4 Claims. (Cl. 92-36) The presentinvention relates to a screening device for screening suspensions,particularly fibrous suspensions, in the form of a rotary cylindricvibratory screening drum which is elastically suspended and consists ofa cylindric shell and a central pipe carrying the same, a

drive shaft provided with eccentric weights being rotatably mounted insaid pipe.

Rapid eccentric movements (preferably about 1200 a minute) are impartedto the screening drum by the eccentric weights located on the driveshafts. The object of the invention is to provide a screening devicewith vibratory parts of small weight in order that bearings and othervibratory parts shall be subjected to as small stresses as possible andto obtain a construction which is so stable that natural oscillationsand thus the risk of ruptures in the material are prevented.

The screening drum according to the invention may be arranged in atrough to which the suspension to be screened is delivered and thematerial that has passed through the shell of the drum may leave thedrum through openings in the end walls of the drum. Spraying pipes maybe inserted through the end walls for spraying away the coarse materialcollecting on the outer surface of the shell to a conveying channelsituated above the drum. The drum with the central pipe may be mountedin journal bearings which are carried by compression springs. Thecentral pipe of the drum preferably arranged to carry the shell of thedrum by the intermediary of a staying device, connecting the middleportion of the shell with the central pipe. Said staying device mayconsist of two wall surfaces issuing from a point on the middle portionof the shell and converging conically towards each end wall.

An embodiment of the screening device according to the invention isillustrated in the accompanying drawings.

Fig. 1 is a longitudinal section of a screening device according to theinvention. Fig. 2 is a cross section on line II-II in Fig. 1.

By reference to the drawings the reference character I designates atrough, into which the fibrous suspension flows through a channel 2 andis screened through the perforated shell 3 of the screening drumimmersed in the fibrous suspension. The screened fibrous suspensionflows out through openings in the end walls of the screening drum and isled off through the pipes 4. The coarse fibres which do not pass throughthe perforated shell 3, accompanying the drum and are by means of waterfrom the spraying pipes 5 which are inserted through the end openingsand do not participate in the rotation of the drum, flushed from thedrum shell off to a conveying channel located above the drum. The screenshell is carried by the pipe I within which the shaft 9 which isprovided with eccentric weights 8, is mounted. On the pipe 1 there aretwo hoppershaped walls In facing one another and carrying the stay pipesI I on which the perforated shell 3 is fixed. The end walls l2 areprovided with outlet openings and are fixed to the ends of said staypipes. Packing rings l3 are provided between the screening drum and thetrough I. The screening drum is carried by the bearings I l which reston the compression springs I5. The screening drum may be rotated by thegear l6 which is driven by the motor I! via the flexible coupling l8.The shaft 9 with the eccentric weights is connected to a motor l9 bymeans of the flexible coupling 20.

When the motors l1 and [9 are set in rotation the screening drum, due tothe eccentric weights 8, begins to vibrate rapidly, being at the sametime slowly rotated by the motor IT. The rapid vibrations imparted tothe screening drum subject the material of the drum to heavy stressesdue to the resistance of the liquid and the weight of the vibratoryparts. Therefore, the above described device in which the screeningshell 3 is supported in the middle by means of the walls "I ensures astable and durable construction.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. Apparatus for screening liquid suspensions such as a fibroussuspension comprising a trough for receiving the suspension, a screeningdrum in said trough adapted to be at least partly immersed in thesuspension and being provided with an outlet for screened material in atleast one end wall thereof, a hollow shaft arranged coaxially with andextending through and supporting said drum, elastic journals at oppositesides of said drum mounting said shaft, said journals being axiallyaligned with the common axis of said shaft and drum means for rotatingsaid shaft, a second shaft arranged coaxially within said hollow shaft,said second shaft being loaded eccentrically with respect to its axis,bearing means carried by said hollow shaft for journalling saideccentrically loaded shaft, and means for rotating the latter to therebyimpart vibratory motion to said hollow shaft and drum through saidbearing means.

2. Apparatus for screening liquid suspensions 3 as defined in claim 1wherein said hollow shaft is provided with substantially radiallyextending supporting means, said supporting means being connected tosaid drum at the middle portion of the latter and constituting the solesupport be tween said shaft and drum.

3. Apparatus for screening liquid suspensions as defined in claim 2wherein said supporting means is constituted by a pair of wall surfacesissuing jointly from a line at the mid-plane of said drum, each of whichsurfaces converges conically toward said end walls.

4. Apparatus for screening liquid suspensions such as a fibroussuspension comprising a trough for receiving the suspension, a screeningdrum in said trough adapted to be at least partly immersed in thesuspension and being provided with an outlet for screened material in atleast one end wall thereof, hollow shaft means arranged coaxially withand supporting said drum, elastic journals at opposite sides of saiddrum mounting said shaft means, said journals being axially aligned withthe common axis of said shaft means and drum, a second shaft arrangedcoaxially within said hollow shaft means, said second shaft being loadedeccentrically with respect to its axis, bearing means within said hollowshaft means journalling said second shaft, and means for rotating saidsecond shaft thereby to impart vibratory motion to said hollow shaftmeans and drum through said bearing means.

KARL ROLAND LINDBLAD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

